1
: a trigonometric function that for an acute angle is the ratio between the leg adjacent to the angle when it is considered part of a right triangle and the hypotenuse
2
: a trigonometric function cos θ that for all real numbers θ is given by the sum of the alternating series {latex}1 - \frac{x^2}{2!} + \frac{x^4}{4!} - \frac{x^6}{6!} + \frac{x^8}{8!} - \dots{/latex} and that is exactly equal to the cosine of an angle of measure θ in radians
Examples of cosine in a Sentence
Recent Examples on the Web
The Fourier transform does this for all possible frequencies, multiplying the original function by both sine and cosine waves.
—
Shalma Wegsman, Quanta Magazine, 3 Sep. 2025
The stronger the cosine transformation, the more compressed the final result.
—IEEE Spectrum, 17 June 2025
In the case of something basic, such as the sine or cosine functions used in trigonometry, that geometry is a simple circle.
—Ramin Skibba, Scientific American, 13 May 2025
These approaches rely on mathematical functions like squaring, adding, or multiplying, rather than irrational numbers, radicals, or functions like sine and cosine.
—Jack Beresford, MSNBC Newsweek, 1 May 2025
Housed in a steel chassis, the motor incorporates a programmable microprocessor with a D/A converter to provide low-distortion sine and cosine waves that are used to turn the motor.
—Mark Sparrow, Forbes.com, 11 Apr. 2025
During retrieval, the system converts the user's query into an embedding using the same neural model, then searches the vector database for chunks whose embeddings have the highest cosine similarity to the query embedding.
—Meghana Puvvadi, Forbes, 25 Feb. 2025
Six hundred years ago, mathematicians were building tables of sines and cosines, which were needed for navigation, but these can now be generated by computers in seconds.
—Matteo Wong, The Atlantic, 4 Oct. 2024
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Shalma Wegsman, Quanta Magazine, 3 Sep. 2025
The stronger the cosine transformation, the more compressed the final result.
—IEEE Spectrum, 17 June 2025
In the case of something basic, such as the sine or cosine functions used in trigonometry, that geometry is a simple circle.
—Ramin Skibba, Scientific American, 13 May 2025
These approaches rely on mathematical functions like squaring, adding, or multiplying, rather than irrational numbers, radicals, or functions like sine and cosine.
—Jack Beresford, MSNBC Newsweek, 1 May 2025
Housed in a steel chassis, the motor incorporates a programmable microprocessor with a D/A converter to provide low-distortion sine and cosine waves that are used to turn the motor.
—Mark Sparrow, Forbes.com, 11 Apr. 2025
During retrieval, the system converts the user's query into an embedding using the same neural model, then searches the vector database for chunks whose embeddings have the highest cosine similarity to the query embedding.
—Meghana Puvvadi, Forbes, 25 Feb. 2025
Six hundred years ago, mathematicians were building tables of sines and cosines, which were needed for navigation, but these can now be generated by computers in seconds.
—Matteo Wong, The Atlantic, 4 Oct. 2024
Cite this Entry
“Cosine.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/cosine. Accessed 31 Oct. 2025.
Copy CitationKids Definition
cosine
noun
co·sine
ˈkō-ˌsīn 
: a trigonometric function that is the ratio between the side next to an acute angle in a right triangle and the hypotenuse
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